From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [63.81.120.155] (helo=imap.sh.mvista.com) by bombadil.infradead.org with esmtp (Exim 4.68 #1 (Red Hat Linux)) id 1JeBuS-0002bd-1o for linux-mtd@lists.infradead.org; Tue, 25 Mar 2008 16:22:00 +0000 Message-ID: <47E926FB.3030900@ru.mvista.com> Date: Tue, 25 Mar 2008 19:23:23 +0300 From: Sergei Shtylyov MIME-Version: 1.0 To: Laurent Pinchart Subject: Re: OF compatible MTD platform RAM driver ? References: <200803101606.39184.laurentp@cse-semaphore.com> <200803251536.17795.laurentp@cse-semaphore.com> <47E91A5B.1060406@ru.mvista.com> <200803251651.42608.laurentp@cse-semaphore.com> In-Reply-To: <200803251651.42608.laurentp@cse-semaphore.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: ben@simtec.co.uk, linuxppc-dev@ozlabs.org, linux-mtd@lists.infradead.org, David Gibson List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Laurent Pinchart wrote: >>>We're talking about a very specific type of RAM, used for permanent storage >>>with a battery backup. The RAM is really meant to be used as an MTD device >>>and as such I think it makes sense to describe it as an mtd-compatible device >>>on the local bus. >>>What about the following definition for the RAM node ? >>> nvram@2,0000 { >> Note that there's a OF "device_type" of "nvram", so your (generic) device >>name seems to add some mess. (IIRC, that OF device type didn't actually >>represent a "real" device, and only served to provide access to NVRAM for OF). > Ok. Well, I might have gone too far here -- it should be a real device (spec'ed in Device Support Extensions recommended practice). It's just that the spec didn't mention "reg" property, only "#bytes" (the device capacity). So, it may be worth considering... >>> compatible = "mtd,ram"; >> The part before comma should be a company name or a stock ticker. What did >>you mean here? > I didn't know that. Let's say I meant "mtd-ram" :-) >>> reg = <2 0x0000 0x00100000>; >>> bank-width = <2>; >>> }; >>>Or should the node have a device-type property of either 'ram' or 'rom' with >>>the compatible property just referencing MTD ? >> The "device_type" properties are not required and their further creation >>has been discouraged on liunxppc-dev. > What about > mtdram@2,0000 { > compatible = "mtd-ram"; > reg = <2 0x0000 0x00100000>; > bank-width = <2>; > }; > ROMs could use "mtd-rom" for their compatible property. Heh, there was a whole company against mentioning "mtd" when we started working on this (of course, the first idea was to call the flash device type "mtd"). I don't think "mtd" looks good here -- I'd suggest "flash-ram" (if this is just a linearly mapped NVRAM). > Best regards, WBR, Sergei